This invention relates to an electrostatic erasing abrasionproof coating and method for forming the same.
Abrasion-proof coatings are formed over surfaces which has a tendency to take scratches due to external rubbing actions. The surface of glass plates which may be used for transmitting light therethrough is a typical example of such a surface. Contact image sensor, which have been recently developed, are suitable for use in compact facsimile machines, copying machines or the like. The image sensor makes direct contact with an original and scans the surface of the original by moving relative to this.
An example of the contact image sensor is illustrated in FIG. 1. The sensor comprises a glass substrate 1, a photosensitive semiconductor device 2, a transparent protective layer 3, an adhesive layer 4, an ITO film 5 and a glass pane 6. An original bearing an image to be sensed is placed in contact with the external surface of the glass pane 6. The ITO film, which is a transparent conductive film, is grounded for the purpose of canceling out electrostatic charges collected on the contact surface of the pane 6 due to rubbing action between the original 9 and the glass pane 6. In case of treatment of usual papers, the size of scratches may be of the order of 1 micron meter or less so that the performance of the sensor is not substantially deteriorated by the scratches. However, if a staple is held to a paper to be telefaxed, the paper may give scratches of substantial size which degrade the quality of the transmission. Furthermore, the use of the ITO film for canceling out static electricity increases the size and the production cost of the device.